Removes warnings from java-17 javadoc.

Update Displayable with displayableDuration.

See merge request !1

- Internal naming in DiffStringUtil.

- Add more control chars for terminal control.
   * Terminal control/restore, clear and reset terminal.
   * Separate Terminal Control and Terminal Input.
- Utility for common ctrl-* inputs.
- Utility method for unicode.
- Document T61Charset.

And have a secondary method to compare positionally.

- only supports default and urdu.